Integrated circuits employ active and passive elements to perform any calculating function. Active elements, such as transistors and varactor diodes, are capable of exhibiting a voltage, current or power gain in response to an external signal. The passive elements, such as resistors and capacitors, do not exhibit a voltage, current or power gain in response to external signals.
The application of active and passive elements within integrated circuits permits the integrated circuits to perform complex calculating tasks.
Because multiple integrated circuits are necessary to perform complicated tasks, the integrated circuits must act in conjunction with each other. The individual integrated circuits are affixed to a passive carrier which includes the passive circuitry to link the multiple integrated circuits. As the capability of the affixed integrated circuits increased, it became necessary to link multiple passive carriers. The linking of multiple passive carriers has been accomplished by employing wire mesh resilient contact elements or buttons. The buttons are pressed into holes in an insulating board which is then sandwiched between passive carriers to provide the electrical linking of the passive carriers.
Traditionally, solder joints have been used to provide the mechanical and electrical interconnection of active components to passive carriers. While soldering is a well-known and widely accepted means of providing electrical interconnections, soldering suffers from substantial disadvantages. Large temperature fluctuations can cause the structure of the solder joint to fail. The structural failure of a solder joint results in a failure of the electrical connection. Solder joints are also vulnerable to failure from repeated mechanical flexing which results from the use of the connections outside of a laboratory environment.
Recent developments in the electronics industry have encountered further limitations of solder joints. The miniaturization of active integrated circuits has resulted in an increased density of interconnections per unit area within the electronic devices. The physical size of a solder joint and the accessibility of the site of the joint have become limiting factors in the suitability of soldered interconnections. The size limitations of the solder connections requires that the interconnections extend beyond the periphery of the integrated circuits, thereby wasting valuable space within the device.
In addition, the creation of the hundreds of solder joints necessary to join multiple active components to a passive substrate is extremely labor intensive. There is a substantial introduction of error into an electrical system through the requirement of such labor. Further, upon failure of a single soldered interconnection, the entire component must be unsoldered so that the interconnection can be replaced or repaired. Therefore, the cost of repairing a failed interconnection may exceed the cost of the active component. This results in the disposal of valuable, working components due to the inability of the interconnections to be easily repaired.
As the size of the integrated circuits has been reduced, the density of elements has increased. This increased density has resulted in an increased density of active integrated circuits per unit area.
The pin grid array was developed to accommodate the increased density of inputs and outputs to the active integrated circuit. However, the pin grid arrays are subject to limitations arising from the ability to operably connect hundreds of pins within a small area. In addition, upon the failure of a single pin, each interconnection of the array must be broken. Therefore, repair of a failed interconnection is expensive.
In place of the pin grid array, pad grid arrays have been employed to connect the active components to a passive carrier. Pad grid arrays provide surface contacts which are blind soldered to connect the active component to the passive carrier. However, the contacts of pad grid arrays require close dimensioned tolerances so that the blind solder joint effectively connects the elements. If an interior joint does not exhibit sufficient integrity, each pad of the entire grid must be unsoldered so that the connection can be repaired.
The connection of active elements to passive carriers has developed from traditional soldered connections, to pin grid arrays and finally to pad grid arrays. Paralleling this development, the interconnection of passive carriers has evolved to include the use of resilient contact elements secured within a retainer.
Therefore, a need exists for providing a mechanical and electrical interconnection system capable of withstanding large temperature fluctuations and mechanical stresses between an active integrated circuit and a passive substrate. In addition, the need exists for a mechanical and electrical interconnection system which is neither labor intensive nor requires an interconnection area larger than the active integrated circuit.